13 December 2011

Dow Electronic Materials develops stannic chloride as tin precursor for GeSn films

Dow Electronic Materials, a business unit of Dow Advanced Materials, has introduced a stannic chloride precursor, which it claims is the first industrially viable, electronic-grade tin precursor for the generation of germanium tin (GeSn) films for electronics. Until now, production of GeSn by chemical vapor deposition (CVD) has been limited to R&D-scale use because only specialized and cost-prohibitive precursors have been available, says the firm.

Tin-containing materials are currently in demand as the electronics industry seeks ways to increase transistor speeds. In response, Dow Electronic Materials has introduced an electronic grade of the tin CVD precursor stannic chloride, which has been used by the nanoelectronics research center Imec of Leuven, Belgium for the growth of GeSn for use in stressors, high-mobility channels, and other features of future semiconductor devices.

“We found a tin precursor that enables the industrial production of GeSn for future-generation electronic devices,” says Egbert Woelk, technology and applications manager at Dow Electronic Materials. “Together with our VAPORSTATION Central Delivery System, we have a turn-key solution to deliver our new tin precursor to any CVD tool on the market,” he adds. “This removes all barriers to using the new GeSn CVD process on a large scale in the latest-generation CVD tools.” In the past, GeSn CVD was limited to using deuterated stannane (SnD4), which is costly to make and not available on a commercial basis.

Silicon germanium (SiGe) is a desirable material for electronics and optoelectronics manufacturers, and the addition of tin increases the speed of transistors made from this material, says Dow Electronic Materials. There is a growing interest in thin germanium or germanium-silicon materials containing tin to enhance semiconductor structures, such as the high-mobility channel that conducts current in transistors, and photonic devices such as LEDs.

Dow says that the viability of its material has been confirmed in a new CVD process developed by Imec. Using stannic chloride supplied by Dow Electronic Materials, Imec has demonstrated the material’s viability in an industrial CVD process, overcoming the barrier of tin’s propensity to etch deposited material. Imec has produced high-content germanium tin epitaxial films (>8% tin content) with outstanding electronic and structural quality (B. Vincent et al., Appl. Phys. Lett. 99 (2011), 152103). According to Imec, the CVD-grown GeSn layer can also be used as a high-mobility channel material on germanium. A strained GeSn channel on germanium is also a possible candidate to be used in the device channel of future Ge-based metal-oxide semiconductor field-effect transistor (MOSFET) devices.

“The CVD growth of GeSn with commercially available precursors will boost the research on high-mobility MOSFETs,” says Imec’s R&D manager Roger Loo. “Besides, it opens new routes for group-IV semiconductors research in other fields, such as photonics (having an indirect-to-direct-bandgap transition expected for about 10% Sn incorporated in monocrystalline GeSn alloys) and photovoltaics (ternary SiGeSn alloys),” he adds. “The good results that we achieved with stannic chloride precursor convince us to continue our successful collaboration with Dow Electronic Materials.”

Imec presented the results of the development work at The 2nd GeSn Workshop: GeSn Developments for Future Applications, held in late August in conjunction with the 7th International Conference on Si Epitaxy and Heterostructures 2011 (ICSI-7) in Leuven.

Tags: Dow Electronic Materials MOSFETs CVD

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